This invention pertains to a flexible joint joining two moveable, independently hinged, aircraft surfaces and, more particularly, to a flex joint employing a spherical bearing.
Modern aircraft lift surfaces, e.g. a swept wing, may have a trailing edge whose plan view projection is two intersecting lines. In order to provide a continuous, faired flap or moveable surface of equal chord length beyond the intersection in the trailing edge, it is necessary to accommodate two contiguous flap segments which rotate about different hinge lines. In addition to the fairing problem, it is necessary to join the two flap segments with a suitable flexible link capable of transmitting point loads, while rotating about several axes, in order to keep the two flap sections moving at the same rate. Each flap section is actuated by two hydraulic cylinders. One cylinder from each section is supplied by one hydraulic system and the remaining two cylinders from another. If one hydraulic system fails, each flap section is actuated by a single cylinder from a common supply and the point loads across the flexible joint become quite high.
Spherical roller bearings, when subjected to high thrust loads, have a tendency to screw out the rollers and inner race due to their inherent geometry. Self-aligning spherical bearings with the bearing surface made from fabric lining such as Teflon (polytetrafluoroethylene) are used extensively in aircraft service where surface speeds are low and load factors are moderate. Spherical bearings are particularly attractive as they can be designed to provide long life, self lubrication, self-alignment, and generally do not experience catastrophic type failures, e.g. seizure. However, spherical bearings, while capable of carrying some thrust load, are inherently radial bearings. Furthermore, the outer race of the spherical bearing is difficult to support when subjected to high thrust loads.
A ball pivot thrust bearing was invented that effectively joins two adjacent, independently hinged moveable control surfaces structurally.